Colors that are opposite each other on the color wheel are considered to be complementary colors (example: red and green).
The high contrast of complementary colors creates a vibrant look especially when used at full saturation. This color scheme must be managed well so it is not jarring. Complementary colors are tricky to use in large doses, but work well when you want something to stand out. Complementary colors are really bad for text.
Analogous color schemes use colors that are next to each other on the color wheel. They usually match well and create serene and comfortable designs. Analogous color schemes are often found in nature and are harmonious and pleasing to the eye.
Make sure you have enough contrast when choosing an analogous color scheme. Choose one color to dominate, a second to support. The third color is used (along with black, white or gray) as an accent.
The third set of hues are known as tertiary or intermediate colors. These hues are made by mixing adjacent primary and secondary hues. The six tertiary or intermediate colors are yellow-green, blue-green, blue-violet, red-violet, red-orange, and yellow-orange.
Note that the names for the tertiary colors always begin with the primary color then the secondary color; yellow-orange not orange-yellow, for example.
A triadic color scheme uses colors that are evenly spaced around the color wheel. Triadic color harmonies tend to be quite vibrant, even if you use pale or unsaturated versions of your hues.
To use a triadic harmony successfully, the colors should be carefully balanced - let one color dominate and use the two others for accent.